It is known in the art of electroplating to use frames on which are removably anchored plates or the like articles to be plated, for holding them while they are being submerged in large acid tanks or baths, e.g. for creating printed circuit boards.
In applicant's U.S. Pat. No. 5,904,820 issued May 18, 1999, there was disclosed and claimed a holding clamp for releasably holding an article to be submerged in a liquid solution bath ahead of a submerged anode bar and to be electroplated therein. This patented holding clamp, destined to downwardly depend from an overlying cathode frame bar, comprises a first and a second elongated arm members made of an electrically conducting material and each defining a lower portion coated with a fluid-tight and electrically insulating sleeve, and an upper and a lower end, the first arm member to be fixedly attached to the cathode frame bar at its upper end, the second arm member being shorter than the first arm member and being pivotally attached to the first arm member and being pivotable between a first limit position in which the lower ends are spaced from one another and a second limit position in which the lower ends abut against one another, the first arm member having electrical current conduction means physically accessible at its lower end. Biasing means biases the arm members lower ends against one another, and a lever member pivotally attached to an intermediate section of the first arm member and located entirely above the first and second arm member sleeves at all times selectively forcibly pivotally biases the second arm member into the first limit position against the action of the biasing means. In this way, the first and second arm members are destined to frictionally hold the article to be electroplated between their lower ends when the second arm member is in its second limit position, thus allowing current to be conducted through the conduction means into the article, with the first and second arm member lower portions destined to be submerged in the solution at the most partially up their sleeves.
Such a holding clamp device is very efficient for holding thin single layer planar articles. However, recent technical developments in the printed circuit boards have brought about thicker, multiple layer printed boards. Because of their greater overall thickness, the jaw studs of the prior art holding clamps are much more spread apart than before. Since the relative movement between the two jaws is a pivotal one about a circle of an arc, when the jaws are opened from their closed condition, the jaws do not remain parallel to one another and accordingly, the studs become eventually axially offset relative to one another. This means that electrical conduction between the studs from the two opposite jaws from a given clamp, becomes compromised in a progressively increasing fashion as the jaws are progressively pivoted away from one another.
In applicant's co-pending parent application, Ser .No. 09/497,704, there is disclosed a holding clamp for releasably holding a thickened planar article to be submerged in a liquid solution bath ahead of a submerged anode bar and to be electroplated therein, said holding clamp destined to downwardly depend from an overlying cathode frame bar, said holding clamp comprising: a) an elongated main arm member, made from an electrically conducting material, and defining first and second opposite end portions; b) a pair of first and second tubular bar members, each defining an outer end portion coated with a fluid-tight and electrically insulating sleeve and an opposite inner end portion, each bar member outer end portion having a transverse terminal stud projecting therefrom, said first bar member anchored at its said inner end portion to said main arm member first end portion parallel thereto; c) a rail member, integral to an intermediate section of said main arm member and slidably engaged by said second bar member inner end portion, wherein said second bar member is maintained by said rail member parallel to said first bar and wherein said second bar member is movable relative to said first bar member while continuously remaining parallel thereto, while the pair of said terminal studs remain coaxially aligned; d) a first biasing member, continuously biasing said first and second bar members toward one another; and e) a second biasing member, for discretely biasing said second bar member away from said first bar member, against the continuous bias of said first biasing member.
In application Ser. No. 09/497,704, the first biasing means includes at least one pair of coil springs, hookingly interconnecting said first and second bar members. The second biasing member includes an arcuate cantilever member defining an engagement leg and an opposite elongated actuation leg, said engagement leg extending between said first and second bar members within their common plane, a pivotal linkage assembly integral to said main arm member and pivotally mounting an intermediate section of said arcuate cantilever member; wherein upon pulling force actuation of said actuation leg to move the latter away from said main arm member, pivotal motion of said cantilever member will bring about frictional engagement of said cantilever member engagement leg against said second bar member for displacement of the latter away from said first bar member.
A problem that appears once and a while is the vibrations generated by the conventional vibrators used in the acid bath tank, to remove air bubbles that may have struck to cavities on the circuit boards during their lowering into the volume of acid. These vibrations may sometimes be important enough to bring about accidental progressive frictional release of the circuit board from the pair of studs between which the circuit board is taken in sandwich. This is undesirable.